Early Mount Wilson years

On his way to Mount Wilson in late summer 1919, Hubble stopped for a visit at Lick Observatory atop Mount Hamilton, southeast of San Francisco. By the late 1910s, the small number of professional astronomers pursuing observations of the nebulae were concentrated at the Lick and Mount Wilson observatories in

California and at Lowell Observatory in Arizona, where Slipher carried on his radial velocity program. Curtis, the chief expert on spiral nebulae at Lick, remained there until shortly after the Great Debate with Shapley in 1920. If only it were Lick, and not Mount Wilson, with the superior telescopes, Hubble might have preferred to establish himself there. Both his scientific interest in the nebulae and his conservative approach would have fit nicely with the outlook of Lick astronomers — a cautious outlook Shapley referred to, somewhat derogatorily and unfairly, as the ''Lick state of mind.''

On 3 September, Hubble presented himself at the Mount Wilson offices, housed in a white neo-classical building on Santa Barbara Street in Pasadena. He joined a dedicated and hard-working staff. Shapley was not the only one rushing from data gathering to data analysis and back to more data gathering; astronomers who worked there at the same time recalled an intense level of activity and a memorable ''spirit of research.'' Hale, the observatory's guiding spirit, still appeared at his Santa Barbara Street office, although he frequently traveled to Washington; it would be another four years before ill health forced him to stay away from the hub of activity he so much enjoyed.

Hubble lived in Pasadena boardinghouses and settled finally in a house he shared with a Caltech humanities professor and a seismologist employed by the Carnegie Institution, Mount Wilson's parent institution. It was the living on the mountaintop, however, that provided a pleasant sense of family and ritual. The ''Monastery'' building of Hubble's day housed up to a dozen astronomers in dormitory style rooms. At the other end of the building from the rooms stood a library with a fireplace and view over the San Gabriel valley, and a dining room, to which astronomers and their assistants were summoned by a bell.

Hubble's first opportunity to observe with the 100-inch telescope arrived in mid-October. The massive telescope, weighing more than 100 tons, was mounted under a sheet-metal dome 100 feet high and 95 feet in diameter. Electric motors controlled the opening and closing of the dome shutter or ''slit,'' the rotation of the dome to allow the slit and telescope to view different parts of the sky, and the motion of the telescope itself as it compensated for the Earth's rotation.

Hale and the Mount Wilson astronomers had waited a long time for the installation of the 100-inch. The financial backer, John D Hooker, had made his original bequest in 1906. The Saint-Gobain glassworks in Paris had cast the glass disk to back the telescope's mirror in August 1907, and had shipped it across the Atlantic. After some uncertainty over the disk's usability, due to bubbles that had formed during annealing, work had begun on grinding and polishing it. Then the figured and silvered disk had arrived at the mountaintop for a first attempt at mounting in July 1917. The telescope finally saw ''first light'' more than ten years after Hooker's bequest, in November 1917.

In 1919, the year Hubble earned his first ''run'' with the 100-inch, janitor Milton Humason was promoted to night assistant thanks in part to Harlow Shapley's support. Humason, a down-to-earth but conservative character, quickly fell under Hubble's spell, addressing him from the first as ''Major.'' Humason appreciated Hubble's care for the telescope and photographic equipment and his well thought out observing plan. Their working relationship got off to a strong start one night when clouds halted Hubble's observing and the astronomer, to Humason's surprise, asked if he could join Humason and members of the work crew in a game of cards.

In a letter to Barnard at Yerkes early in 1920, Hubble wrote that his plan was to learn all he could about the galactic nebulae — that is, the nebulous objects scattered among the stars and clusters of our own Milky Way system. To push his plan forward as quickly as possible, Hubble did not rely solely on his allocation of time at the 100-inch, but also used the 60-inch and a smaller telescope with a wide-angle lens, suitable for photographing large swaths of sky. But in the same year, Hubble also re-wrote his hastily-completed doctoral dissertation, at the insistence of Yerkes director Frost, and this activity prodded him to think as well about the non-galactic nebulae, those usually called spirals.

Hubble emphasized in the published version of his dissertation that the high velocities of the nebulae moving generally away from the Milky Way made it unlikely that these objects could in any sense pertain to the local system. He favored the hypothesis ''that the spirals are stellar systems at distances to be measured often in millions of light years.'' However, he noted, ''Extremely little is known of the nature of the nebulae, and no significant classification has yet been suggested; not even a precise definition has been formulated.''9 Thus both galactic and spiral nebulae filled his thoughts as he returned to civilian life and began formulating a research program.

Hubble was still enjoying the heady adventure of his first year with the world's largest telescope when, at the observatory site one evening, he met the woman who would become his wife. Grace, the sister-in-law of a visiting colleague from Lick Observatory, was married at that time, so both she and Hubble may have checked their enthusiasm at their first encounter. She later recalled feeling profoundly impressed by his good looks and serene detachment—a detachment which others viewed in a less positive light as aloofness.

Grace, petite and vivacious, was the same age as Hubble. She was born to a wealthy California businessman and his wife, the Burkes, and attended a private girls' school in Los Angeles. She graduated from Stanford University in 1912. Astronomers who knew her later described her seriously as an ''intellectual giant.''10 She had concentrated her studies in English, and easily cultivated the friendship of prominent artists and writers.

From her diary entries and from remarks made by her friends, it appears that Hubble drew strength from her cool self-possession—a trait that he cultivated, but that she apparently expressed naturally. She, on the other hand, enjoyed his intellectual companionship and the opportunity to help manage his public image and career.

A year after Grace met Hubble, her husband, a geologist, died in an accident while attempting to retrieve a sample from a coal mine near Sacramento. The couple had had no children. Shortly thereafter, Hubble began a discreet courtship of Grace, away from the observatory, usually visiting her at her parents' home in Los Angeles.

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